Elucidating the physiological and ecological traits of filterable bacteria

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H05620
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Applied microbiology
• Research Institution: National Institute of Advanced Industrial Science and Technology (2017-2018); National Institute of Genetics (2015-2016)
• Principal Investigator: Nakai Ryosuke 国立研究開発法人産業技術総合研究所, 生命工学領域, 研究員 (90637802)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 応用微生物 / 微生物生態

Outline of Final Research Achievements

The occurrence of ultra-small filterable bacteria capable of passing through 0.2-micrometer-pore-size filters has been reported recently. In this study, we determined the growth characteristics, physiological and biochemical properties, and genomic structures of two representative filterable strains (novel alphaproteobacterium IZ6 and Oligoflexus tunisiensis Shr3), isolated from terrestrial environments. As a result, functional genes involved in nitrogen cycle, such as nitrogen fixation and denitrification, were detected from the genome information, and the nitrogen fixation ability was confirmed by a culture experiment using the novel strain IZ6. Furthermore, metagenomic analysis of filterable bacterial populations present in environmental samples revealed the existence of novel metabolic pathways in uncultured lineages. Thus, it was disclosed that microorganisms with novel biological functions exist in the neglected filterable fraction.

Free Research Field

微生物学

Academic Significance and Societal Importance of the Research Achievements

微生物の最小サイズは一般に0.2マイクロメートル前後とされ、医薬・食品業界や生物学諸分野において孔径約0.2マイクロメートルのフィルターを用いた濾過除菌が汎用される。本研究はこの除菌フィルターを通過する新規な極小細菌群を網羅的に調べたことに学術的意義がある。同時に、そこにユニークな生物機能を有する細菌が見出されたことから、今後の生物資源・遺伝子資源の探索において、濾過性細菌が有力候補の一つになることが明確化したことにも意義があると考える。